DNA Mutations Types & their effects

Mutations are heritable changes in genetic information. What are Mutations? Mutations are heritable changes in genetic information.

What Causes Mutations? Mutagens: certain substances or conditions that can create a greater rate of mutation. Some examples include: Viruses High temperatures Radiation (UV rays) Chemicals (mustard gas, DDT, Agent-Orange)

All mutations fall into two basic categories: Types of Mutations All mutations fall into two basic categories: Gene mutations produce changes in a single gene. 2. Chromosomal mutations produce changes in whole chromosomes.

Gene Mutations Point mutations involve changes in one or a few nucleotides. This is because they occur at a single point in the DNA sequence. They generally occur during replication. If a gene in one cell is altered, the alteration can be passed on to every cell that develops from the original one.

Types of Gene Mutations Point mutations are caused by substitutions.

Gene Mutations - Substitution In a substitution, one base is changed to a different base. Substitutions usually affect no more than a single amino acid, and sometimes they have no effect at all.

Gene Mutations – Frameshifts: Insertions and Deletions Insertions and deletions are frameshift mutations in which one base is inserted or removed from the DNA sequence. If a nucleotide is added or deleted, the bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation.

Chromosomal Mutations Chromosomal mutations involve changes in the number or structure of chromosomes. These mutations can change the location of genes on chromosomes and can even change the number of copies of some genes. There are four types of chromosomal mutations: deletion, duplication, inversion, and translocation.

Chromosomal Mutations - Deletion Deletion involves the loss of all or part of a chromosome.

Chromosomal Mutations - Duplication Duplication produces an extra copy of all or part of a chromosome.

Chromosomal Mutations - Inversion Inversion reverses the direction of parts of a chromosome.

Chromosomal Mutations - Translocation Translocation occurs when part of one chromosome breaks off and attaches to another.

How Do Mutations Affect Genes? The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene function. Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.

Effects of Mutations -Genetic material can be altered by natural events or by artificial means. -The resulting mutations may or may not affect an organism. -Many mutations are produced by errors in genetic processes. -For example, some point mutations are caused by errors during DNA replication. -The cellular machinery that replicates DNA inserts an incorrect base roughly once in every 10 million bases. -Small changes in genes can gradually accumulate over time.

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